Azo moiety containing metal complexes in toners

ABSTRACT

A symmetric 2:1 metal complex represented by the general formula: ##STR1## where R is a hydrogen atom, an alkyl group having from 1 to 10 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an alkoxycarbonyl group having from 2 to 5 carbon atoms, an acyl group having from 2 to 5 carbon atoms, an aminocarbonyl group, an alklyaminocarbonyl group having from 2 to 5 carbon atoms, an alkylsulfonyl group having from 1 to 3 carbon atoms, an aminosulfonyl group, an acylamino group having from 2 to 5 carbon atoms, a nitro group, a cyano group or a halogen atom, m is an integer of from 1 to 4, when m is 2 or more, the plurality of R may be the same or different substituents, Q is --NHCO--Y--Z or --CONH--Y--Z (where Y is an alkylene group having from 1 to 4 carbon atoms, and Z is a quaternary ammonium group), M is a chromium atom or a cobalt atom, and X.sup.⊖ is an anion.

The present invention relates to a metal complex and an electrophotographic toner containing the metal complex.

In electrophotography, it is common to employ a method which comprises forming an electrostatic latent image on a photoconductor made of e.g. a photoconductive material, then developing the latent image with a powder developer to form a visible image, and further fixing the image by heat or a solvent.

As the developer for such electrophotography, it is common to use a mixture comprising fine powder composed of a resin and a coloring agent, which is generally called a toner, and fine glass beads or iron powder, which is generally called a carrier.

The present invention relates to this developing powder called a toner and a novel metal complex useful for the toner.

A photoconductive layer can be positively or negatively charged, and a positively or negatively charged electrostatic latent image can be formed in the photoconductive layer by exposing it with an original overlaid thereon. When a negatively charged electrostatic latent image is developed with a positively charged toner, a positive-positive image corresponding to the original will be formed. However, when a positively charged electrostatic latent image is developed with a negatively charged toner, a negative image of the original, i.e. a positive-negative image, where the black and white tones are reversed, will be obtained. Thus, as electrophotographic toners, there are two types of toners, i.e. one being a positively charged toner and the other being a negatively charged toner.

The present invention relates to a positively chargeable toner.

In general, such a toner is fine powder obtained by mixing a coloring agent such as a dyestuff or a pigment, to a synthetic resin.

In order to positively charge the toner, the electrostatic characteristics of the dyestuff play an important role so that the dyestuff serves not only as a coloring agent but also as an electric charge-controlling agent.

As a positive charge-controlling agent, basic dyestuffs such as Nigrosine have been employed. However, the conventional dyestuffs such as Nigrosine have drawbacks such that there is a substantial variation in the electric chargeability among production lots, and when formed into a toner the durability of the toner for continuous repeated use for photocopying is not good.

The present inventors have conducted extensive researches to solve the above problems, and have found certain metal complexes having a positive charge-controlling ability and good compatibility with resins. It is thereby possible to obtain excellent toners free from the above-mentioned problems.

Namely, the present invention provides a symmetric 2:1 metal complex represented by the general formula: ##STR2## where R is a hydrogen atom, an alkyl group having from 1 to 10 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an alkoxycarbonyl group having from 2 to 5 carbon atoms, an acyl group having from 2 to 5 carbon atoms, an aminocarbonyl group, an alkylaminocarbonyl group having from 2 to 5 carbon atoms, an alkylsulfonyl group having from 1 to 3 carbon atoms, an aminosulfonyl group, an acylamino group having from 2 to 5 carbon atoms, a nitro group, a cyano group or a halogen atom, m is an integer of from 1 to 4, when m is 2 or more, the plurality of R may be the same or different substituents, Q is --NHCO--Y--Z or --CONH--Y--Z (where Y is an alkylene group having from 1 to 4 carbon atoms, and Z is a quaternary ammonium group), M is a chromium atom or a cobalt atom, and X.sup.⊖ is an anion.

The present invention also provides an electrophotographic toner containing the metal complex of the formula I as an electric charge-controlling agent or a coloring agent.

Now, the present invention will be described in detail with reference to the preferred embodiments.

The metal complex of the formula I of the present invention may be prepared in good yield by diazotizing a diazo component represented by the general formula: ##STR3## where R and m are as defined above, by a conventional method, then coupling the resulting diazo compound with a coupling component represented by the general formula: ##STR4## where X.sup.⊖ and Q are as defined above, by a conventional method, to obtain a monoazo compound represented by the general formula: ##STR5## where R, m, X.sup.⊖ and Q are as defined above, and then heat-treating this monoazo compound with a chromium-introducing agent or a cobalt-introducing agent in water or in an organic solvent by a conventional method. As the diazo component of the formula II which may be used in the present invention, there may be mentioned, for instance, 3-chloro-2-aminophenol, 4-chloro-2-aminophenol, 4-bromo-2-aminophenol, 5-bromo-2-aminophenol, 4-iodo-2-aminophenol, 3,5-dichloro-2-aminophenol, 4,6-dichloro-2-aminophenol, 3,4,6-trichloro-2-aminophenol, 4-nitro-2-aminophenol, 5-nitro-2-aminophenol, 6-chloro-4-nitro-2-aminophenol, 4-chloro-5-nitro-2-aminophenol, 4-chloro-6-nitro-2-aminophenol, 6-bromo-4-nitro-2-aminophenol, 4-methyl-2-aminophenol, 4-t-butyl-2-aminophenol, 4-t-octyl-2-aminophenol, 4,5-dimethyl-2-aminophenol, 4-methoxy-2-aminophenol, 4-methyl-5-nitro-2-aminophenol, 4-bromo-5-methyl-2-aminophenol, 4-cyano-2-aminophenol, 4-acetyl-2-aminophenol, 4-methoxycarbonyl-2-aminophenol, 4-aminocarbonyl-2-aminophenol, 4-ethylaminocarbonyl-2-aminophenol, 4-aminosulfonyl-2-aminophenol and 4-propylsulfonyl-2-aminophenol.

As the coupling component of the formula III where Q is --NHCO--Y--Z, there may be mentioned N,N,N-trimethyl-N-[N'-(7-hydroxy-1-naphthyl)carbamoyl]methylammonium chloride, N,N,N-trimethyl-N-[N'-(6-hydroxy-1-naphthyl)carbamoyl]methylammonium chloride, N,N,N-triethyl-N-[N'-(7-hydroxy-1-naphthyl)carbamoyl]methylammonium chloride, N,N-dimethyl-N-ethyl-N-[N'-(7-hydroxy-1-naphthyl)carbamoyl]methylammonium iodide, N,N-dimethyl-N-n-butyl-N-[N'-(7-hydroxy-1-naphthyl)carbamoyl]methylammonium bromide, N,N-dimethyl-N-n-butyl-N-[N'-(6-hydroxy-1-naphthyl)carbamoyl]methylammonium chloride, N,N,N-trimethyl-N-[N'-(7-hydroxy-1-naphthyl)carbamoyl]propylammonium chloride, N,N,N-trimethyl-N-[N'-(6-hydroxy-1-naphthyl)carbamoyl]propylammonium chloride, N,N-dimethyl-N-benzyl-N-[N'-(7-hydroxy-1-naphthyl)carbamoyl]methylammonium chloride, N-methyl-N-[N'-(7-hydroxy-1-naphthyl)carbamoyl]propylpiperidinium bromide, N-methyl-N-[N'-(7-hydroxy-1-naphthyl)carbamoyl]methylmorpholinium chloride, N-[N'-(7-hydroxy-1-naphthyl)carbamoyl]methylpyridinium chloride, and N-[N'-(6-hydroxy-1-naphthyl)carbamoyl]methylpyridinium chloride.

Further, as the coupling component of the formula III where Q is --CONH--Y--Z, there may be mentioned N,N,N-trimethyl-N-2-(3-hydroxy-2-naphthamido)ethylammonium chloride, N,N,N-triethyl-N-2-(3-hydroxy-2-naphthamido)ethylammonium chloride, N,N,N-trimethyl-N-3-(3-hydroxy-2-naphthamido)propylammonium bromide, N,N-dimethyl-N-ethyl-N-3-(3-hydroxy-2-naphthamido)propylammonium chloride, N,N,N-trimethyl-N-4-(3-hydroxy-2-naphthamido)butylammonium chloride, N,N-dibutyl-N-methyl-N-3-(3-hydroxy-2-naphthamido)propylammonium chloride, N-methyl-N-3-(3-hydroxy-2-naphthamido)propylpiperidinium bromide, N-methyl-N-3-(3-hydroxy-2-naphthamido)propylmorpholinium chloride and N-2-(3-hydroxy-2-naphthamido)ethylpyridinium chloride.

The metal complex of the formula I of the present invention thus obtained, has a positive chargeability and excellent compatibility with resins, for example, a polymer of styrene or a substituted styrene such as polystyrene or polyvinyl toluene, a styrene-substituted styrene copolymer, a styrene-acrylate copolymer, a styrene-methacrylate copolymer, a styrene-acrylonitrile copolymer, a polyvinyl chloride resin, a polyethylene, a silicone resin, a polyester, a polyurethane, a polyamide, an epoxy resin, a modified rosin or a phenol resin. Thus, the metal complex can uniformly be dispersed in such a resin and further pulverized into fine powder. Such a fine powder also has positive chargeability.

On the other hand, the metal complex of the present invention has little solubility in water, and scarcely affected by the environmental humidity, thus being capable of maintaining the positive chargeability for a long period of time.

In the formula I, X.sup.⊖ is preferably a halogen ion such as a chlorine, bromine, fluorine or iodine ion.

The toner of the present invention may be prepared by melt-mixing from 1 to 50% by weight of the metal complex of the formula I with 50 to 99% by weight of a synthetic resin, and after the solidification, pulverizing the solidified product by means of a ball mill or other pulverizer. Alternatively, it may be prepared by adding a polymerization initiator to a synthetic resin monomer, incorporating from 1 to 50%, by weight of the monomer, of the metal complex of the formula I thereto, and polymerizing the mixture is a suspended state in water. Other coloring agents or carbon black may also be incorporated. The toner thus obtained will provide an electric charge in a quantity suitable for the development of an electrostatic image due to the friction with the carrier, whereby the quantity of the electric charge can be maintained at a constant level during repeated development operations. The distribution of the electric charge is uniform and can be maintained in a stabilized condition for a long period of time. Accordingly, an image developed by means of this toner, is uniform and has a constant image density, and it is very sharp as compared with the image where a conventional positive toner is used.

Now, the present invention will be described in further detail with reference to Examples. However, it should be understood that the present invention is by no means restricted by these specific Examples.

In the Examples, "parts" means "parts by weight".

EXAMPLE 1

14.4 Parts of 4-chloro-2-aminophenol was mixed with 26 parts of concentrated hydrochloric acid and 400 parts of water, and the mixture was cooled with ice to a temperature of from 0° to 5° C. After an addition of 6.9 parts of sodium nitrite, the mixture was stirred at the same temperature for 2 hours for diazotization. The diazo compound thus obtained was subjected to a coupling reaction by pouring it into a solution of a mixture comprising 300 parts of water, 10 parts of sodium hydroxide and 29.3 parts of N,N,N-trimethyl-N-[N'-(7-hydroxy-1-naphthyl)carbamoyl]methylammonium chloride at a temperature of from 0° to 5° C. Then, a monoazo compound having the following structure was isolated. ##STR6##

This monoazo compound was dissolved in 120 parts of ethylene glycol, and 17.4 parts of sodium chromium salicylate was added thereto. The mixture was stirred at a temperature of from 85° to 90° C. for a chromium-introducing reaction. Then, the mixture was cooled to 30° C., and hydrochloric acid was added to acidify the mixture to an acidity confirmed by Congo Red. Then, the product was isolated at room temperature, and dried under reduced pressure at 50° to 60° C. to obtain 45 parts of chromium complex of the following formula as a blackish blue fine powder: ##STR7## The wavelength at the maximum absorption by this chromium complex was 581 nm as measured in a dimethylformamide solvent.

The coupling component used in this Example was prepared by chloroacetylating 8-amino-2-naphthol in glacial acetic acid with chloroacetic acid chloride by using sodium acetate as an acid binding agent, to obtain 8-chloroacetylamino-2-naphthol, dissolving isolated 8-chloroacetylamino-2-naphthol in acetone, and then blowing gaseous trimethylamine into the solution.

EXAMPLE 2

53.8 Parts of a monoazo dyestuff represented by the formula: ##STR8## obtained in the same manner as in Example 1, was dissolved in 200 parts of methyl cellosolve, and after an addition of 18.2 parts of sodium chromium salicylate, the mixture was stirred at a temperature of from 100° to 105° C. for 2 hours for a chromium-introducing reaction. Then, the mixture was cooled to 20° C., and then treated in the same manner as in Example 1 to obtain 51.2 parts of a chromium complex of the following formula as a black powder: ##STR9##

The wavelength at the maximum absorption by this chromium complex was 594 nm as measured in a dimethylformamide solvent.

The coupling component used in this Example was readily prepared by heating 5-chloroacetylamino-2-naphthol in pyridine.

EXAMPLES 3 to 32

In the same manner as in Examples 1 and 2, symmetric 2:1 metal complexes were obtained. The structures, the wavelengths at the maximum absorption (in dimethylformamide) and outer appearance are shown in Table 1.

                                      TABLE 1                                      __________________________________________________________________________      Examples                                                                             Monoazo compound                                                                             ##STR10##     metalCentral                                                                        solventComplexing                                                                         (nm)absorptionmaximumat                                                        theWavelength                                                                         anceappear-Outer     __________________________________________________________________________            ##STR11##    B: CH.sub.2.sup.⊕N(CH.sub.3).sub.3Cl.sup.⊖                         1             Cr   Ethylene glycol                                                                           576    Black powder          4                                                                                     ##STR12##    B: CH.sub.2.sup.⊕N(CH.sub.3).sub.3Cl.sup.⊖                         3             Cr   Dimethylformamide                                                                         583    Blackish purple                                                                powder                5                                                                                     ##STR13##    B: CH.sub.2.sup.⊕N(C.sub.2 H.sub.5).sub.3Cl.sup..c                         rclbar.       Cr   Ethylene glycol                                                                           592    Black powder          6                                                                                     ##STR14##                                                                                    ##STR15##    Cr   Water      597    Blackish purple                                                                powder                7                                                                                     ##STR16##    B: C.sub.2 H.sub.4.sup.⊕N(CH.sub.3).sub.3Cl.sup..c                         rclbar.       Co   Water      562    Black powder          8                                                                                     ##STR17##                                                                                    ##STR18##    Cr   Methyl cellosolve                                                                         585    Black powder          9                                                                                     ##STR19##    B: CH.sub.2.sup.⊕N(CH.sub.3).sub.3Cl.sup.⊖                                       Co   n-Butanol  560    Black powder          10                                                                                    ##STR20##                                                                                    ##STR21##    Cr   Dimethyl sulfoxide                                                                        592    Black powder          11                                                                                    ##STR22##    B: CH.sub.2.sup.⊕N(CH.sub.3).sub.3Cl.sup.⊖                                       Cr   Formamide Water                                                                           612    Black powder          12                                                                                    ##STR23##                                                                                    ##STR24##    Cr   Ethylene glycol                                                                           587    Blackish purple                                                                powder                13                                                                                    ##STR25##                                                                                    ##STR26##    Cr   Ethylene glycol                                                                           613    Black powder          14                                                                                    ##STR27##    B: CH.sub.2.sup.⊕N(CH.sub.3).sub.3Cl.sup.⊖                                       Cr   Water Dimethylformamide                                                                   608    Black powder          15                                                                                    ##STR28##                                                                                    ##STR29##    Cr   Ethylene glycol                                                                           589    Black powder          16                                                                                    ##STR30##    B: CH.sub.2.sup.⊕N(CH.sub.3).sub.3Cl.sup.⊖                                       Cr   Ethylene glycol                                                                           590    Blackish purple                                                                powder                17                                                                                    ##STR31##                                                                                    ##STR32##    Cr   Water      593    Blackish blue                                                                  powder                18                                                                                    ##STR33##    B: C.sub.3 H.sub.6.sup.⊕N(CH.sub.3).sub.3Cl.sup..c                         rclbar.       Co   Ethylene glycol                                                                           559    Blackish purple                                                                powder                19                                                                                    ##STR34##                                                                                    ##STR35##    Cr   Methyl cellosolve                                                                         592    Black powder          20                                                                                    ##STR36##    B: CH.sub.2.sup. ⊕N(CH.sub.3).sub.3Cl.sup..crclbar                         .             Cr   Diethylene glycol                                                                         588    Blackish blue                                                                  powder                21                                                                                    ##STR37##                                                                                    ##STR38##    Cr   Ethylene glycol                                                                           596    Blackish purple                                                                powder                22                                                                                    ##STR39##    B: C.sub.4 H.sub.8.sup.⊕N(CH.sub.3).sub.3Br.sup..c                         rclbar.       Cr   Methyl cellosolve                                                                         592    Black powder          23                                                                                    ##STR40##    B: CH.sub.2.sup.⊕N(CH.sub.3).sub.3Cl.sup.⊖                                       Cr   Triethanolamine                                                                           582    Black powder          24                                                                                    ##STR41##                                                                                    ##STR42##    Cr   n-Butanol  587    Blackish blue                                                                  powder                25                                                                                    ##STR43##    B: CH.sub.2.sup.⊕N(CH.sub.3).sub.3CH.sub.3                                 SO.sub.4.sup.⊖                                                                       Cr   Ethylene glycol                                                                           594    Black powder          26                                                                                    ##STR44##    B: CH.sub.2.sup.⊕N(CH.sub.3).sub.3Cl.sup.⊖                                       Cr   Ethylene glycol                                                                           593    Black powder          27                                                                                    ##STR45##    B: CH.sub.2.sup.⊕N(CH.sub.3).sub.3Cl.sup.⊖                                       Cr   n-Butanol  592    Black powder          28                                                                                    ##STR46##                                                                                    ##STR47##    Cr   Ethylene glycol                                                                           586    Blackish purple                                                                powder                29                                                                                    ##STR48##                                                                                    ##STR49##    Cr   Methyl cellosolve                                                                         590    Blackish blue                                                                  powder                30                                                                                    ##STR50##    B: CH.sub.2.sup.⊕N(CH.sub.3).sub.3I.sup.⊖                                        Cr   Methyl cellosolve                                                                         593    Black powder          31                                                                                    ##STR51##    B: C.sub.3 H.sub.6.sup.⊕N(CH.sub.3).sub.3Cl.sup..c                         rclbar.       Cr   Ethylene glycol                                                                           585    Black powder          32                                                                                    ##STR52##    B: CH.sub.2.sup.⊕N(C.sub.2 H.sub.5).sub.                                   3Br.sup.⊖                                                                            Cr   Dimethylformamide                                                                         616    Black powder          __________________________________________________________________________

EXAMPLE 33

15.4 Parts of 5-nitro-2-aminophenol was mixed with 26 parts of concentrated hydrochloric acid and 250 parts of water, and the mixture was cooled with ice to a temperature of from 0° to 5° C. After an addition of 6.9 parts of sodium nitrite, the mixture was stirred at the same temperature for 1.5 hours for diazotization. The diazo compound thus obtained was subjected to a coupling reaction by pouring it into a solution comprising 400 parts of water, 10 parts of sodium hydroxide and 39.9 parts of N,N,N-trimethyl-N-3-(3-hydroxy-2-naphthamido)propylammonium methylsulfate at a temperature of from 0° to 5° C. Then, a monoazo compound represented by the formula: ##STR53## was isolated. This monoazo compound was dissolved in 150 parts of methyl cellosolve, and 17.5 parts of sodium chromium salicylate was added thereto. The mixture was stirred at from 90° to 95° C. for 2 hours for a chromium-introducing reaction. Then, the reaction mixture was cooled to 25° C., and hydrochloric acid was added to acidify the mixture. Then, the product was isolated and dried under reduced pressure at a temperature of from 50° to 60° C. to obtain 56 parts of a chromium complex having the following formula as a blackish purple powder: ##STR54## The visible ray absorption spectrum of this chromium complex was measured in a dimethylformamide solvent, whereby the wavelength at the maximum absorption was 599 nm.

The coupling component used in this Example was obtained by reacting methyl 2-hydroxy-3-naphthoate with dimethylamino propylamine in toluene to obtain N,N-dimethyl-N-3-(3-hydroxy-2-naphthamido)propylamine, and converting the amide compound isolated by filtration, with dimethylsufuric acid in methanol, to a quaternary ammonium form. Further, the amide compound may also be readily prepared via 2-hydroxy-3-napthoic acid chloride.

EXAMPLE 34

62.8 Parts of a monoazo dyestuff of the formula: ##STR55## obtained in the same manner as in Example 33, was dissolved in 200 parts of dimethylformamide, and after an addition of 30.5 parts of chromium acetate (45% solution), the mixture was stirred at a temperature of from 100° to 105° C. for 3 hours for a chromium-introducing reaction. Then, the mixture was treated in the same manner as in Example 33 to obtain 54.3 parts of a chromium complex of the following formula as a blackish purple fine powder: ##STR56## The visible ray absorption spectrum of this chromium complex was measured in a dimethylformamide solvent, whereby the wavelength at the maximum absorption was 602 nm.

EXAMPLES 35 to 58

In the same manner as in Examples 33 and 34, metal complexes were prepared. The structures, the wavelengths at the maximum absorption and the outer appearances of these metal complexes are shown in Table 2.

                                      TABLE 2                                      __________________________________________________________________________      Examples                                                                            Monoazo compound                                                                             ##STR57##        metalCentral                                                                        Complexing solvent                                                                       (nm)absorptionmaximuma                                                        t theWavelength                                                                        anceappear-Oute                                                               r                    __________________________________________________________________________     35                                                                                   ##STR58##                                                                                    ##STR59##       Cr   Ethylene glycol                                                                          595    Black powder         36                                                                                   ##STR60##                                                                                    ##STR61##       Cr   Ethylene glycol                                                                          591    Blackish blue                                                                  powder               37                                                                                   ##STR62##                                                                                    ##STR63##       Cr   Dimethylformamide                                                                        601    Blackish purple                                                                owder                38                                                                                   ##STR64##                                                                                    ##STR65##       Cr   Ethylene glycol                                                                          587    Black powder         39                                                                                   ##STR66##                                                                                    ##STR67##       Cr   Water Ethylene                                                                           598col Blackish blue                                                                  powder               40                                                                                   ##STR68##                                                                                    ##STR69##       Co   Ethylene glycol                                                                          572    Blackish blue                                                                  powder               41                                                                                   ##STR70##                                                                                    ##STR71##       Cr   n-Butanol 587    Black powder         42                                                                                   ##STR72##                                                                                    ##STR73##       Cr   Ethylene glycol                                                                          586    Black powder         43                                                                                   ##STR74##                                                                                    ##STR75##       Cr   Ethylene glycol                                                                          593    Blackish blue                                                                  powder               44                                                                                   ##STR76##                                                                                    ##STR77##       Co   Methyl cellosolve                                                                        571    Blackish purple                                                                owder                45                                                                                   ##STR78##                                                                                    ##STR79##       Cr   n-Butanol 590    Black powder         46                                                                                   ##STR80##                                                                                    ##STR81##       Cr   Ethylene glycol                                                                          610    Black powder         47                                                                                   ##STR82##                                                                                    ##STR83##       Cr   Ethylene glycol                                                                          587    Black powder         48                                                                                   ##STR84##                                                                                    ##STR85##       Cr   Ethylene glycol                                                                          592    Blackish  blue                                                                 powder               49                                                                                   ##STR86##                                                                                    ##STR87##       Cr   Dimethylformamide                                                                        595    Blackish blue                                                                  powder               50                                                                                   ##STR88##                                                                                    ##STR89##       Co   Triethanolamine                                                                          568    Blackish purple                                                                owder                51                                                                                   ##STR90##                                                                                    ##STR91##       Cr   Water     590    Black powder         52                                                                                   ##STR92##                                                                                    ##STR93##       Cr   Ethylene glycol                                                                          598    Black powder         53                                                                                   ##STR94##                                                                                    ##STR95##       Cr   Diethylene glycol                                                                        586    Blackish purple                                                                owder                54                                                                                   ##STR96##                                                                                    ##STR97##       Cr   Ethylene glycol                                                                          593    Black powder         55                                                                                   ##STR98##                                                                                    ##STR99##       Cr   Dimethylformamide                                                                        588    Black powder         56                                                                                   ##STR100##                                                                                   ##STR101##      Cr   Water     592    Black powder         57                                                                                   ##STR102##                                                                                   ##STR103##      Cr   Dimethylformamide                                                                        600    Black powder         58                                                                                   ##STR104##                                                                                   ##STR105##      Cr   Ethylene glycol                                                                          594    Blackish blue                                                                  powder               __________________________________________________________________________

Now, the following Application Examples are given to illustrate the toners of the present invention.

Application Example 1

To 5 parts of the chromium complex obtained in Example 1, 100 parts of a styrene-n-butyl methacrylate copolymer and 5 parts of carbon black were added and thoroughly mixed. Then, the mixture was kneaded while heating and melting it. After cooling, the mixture was roughly pulverized in a mixer, and then finely pulverized by a high speed centrifugal pulverizer to obtain a positively chargeable fine toner. The toner was mixed with iron powder having a particle size of from 100 to 150 μm in a weight ratio of 5:100, and the mixture was used for a commercially available copying machine employing a zinc oxide photosensitive material, whereby a clear image free from fogging was obtained. The quantity of the electric charge of the toner was 22 μc/g on an average as measured by a blow off method, and the electric charge distribution was substantially uniform at a level of from 22 to 23 μc/g.

Application Examples 2 to 13

In the same manner as in Application Example 1, toners containing metal complexes and having compositions as identified in Table 3 were prepared. The electric chargeability of these toners was measured. The results are also shown in Table 3.

                                      TABLE 3                                      __________________________________________________________________________                                                                Elec-               Appli-                                                     tric                cation                                                     charge-             Exam-                                                                              Composition of the developer                           abilty              ples                                                                               Metal complex                         Other components (μc/g)           __________________________________________________________________________          ##STR106##                           Styrene-n-butyl methacrylate                                                   copolymer Carbon black Iron                                                    powder carrier                                                                             20 parts 1 part 500                                                            parts                                                                               18.3                    0.2 part                                                                   3                                                                                   ##STR107##                           Phenol resin Polyester resin                                                   Carbon black Iron powder                                                       carrier     12 parts 9 parts                                                               1.5 parts 500                                                                       16.8s                   0.5 part                                                                   4                                                                                   ##STR108##                           Polyethylene wax Ethylene-vinyl                                                cetate copolymer Magnetite                                                                 50 parts 40 parts                                                              50                                                                                  17.3s                   1 part                                                                     5                                                                                   ##STR109##                           Styrene-ethylhexyl methacrylate                                                copolymer Polyester resin                                                      Silicone wax Carbon black                                                      Silicone resin-coated iron                                                     powder carrier                                                                             40 parts 5 parts 4                                                             parts 0.1 part 700                                                             parts                                                                               10.3                    0.1 part                                                                   6                                                                                   ##STR110##                           Styrene-acryl copolymer Carbon                                                 black Glass beads                                                                          20 parts 2 parts                                                               1000 parts                                                                          15.4                    0.2 part                                                                   7                                                                                   ##STR111##                           Styrene-ethyl methacrylate                                                     copolymer Iron powder                                                                      100 parts 2000                                                                 parts                                                                               13.2                    5 parts                                                                    8                                                                                   ##STR112##                           Styrene-butadiene copolymer                                                    Carbon black Iron powder                                                       carrier     50 parts 5 parts                                                               1500 parts                                                                          18.9                    2 parts                                                                    9                                                                                   ##STR113##                           Styrene-n-butyl methacrylate                                                   copolymer C.I. pigment blue-15                                                 Iron powder carrier                                                                        12 parts 0.1 part                                                              500                                                                                 17.4s                   0.5 part                                                                   10                                                                                  ##STR114##                           Polyester resin Carbon black                                                   Iron powder carrier                                                                        50 parts 5 parts                                                               1500 parts                                                                          12.1                    1 part                                                                     11                                                                                  ##STR115##                           Styrene-methyl acrylate                                                        copolymer C.I. pigment black 1                                                 Iron powder carrier                                                                        50 parts 3 parts                                                               1500 parts                                                                          12.8                    1 part                                                                     12                                                                                  ##STR116##                           Epoxy resin Carbon black Iron                                                  powder carrier                                                                             30 parts 3 parts                                                               1000 parts                                                                          11.1                    0.5 part                                                                   13                                                                                  ##STR117##                           Polyvinyl butyral resin Carbon                                                 black Iron powder                                                                          10 parts 1 part 250                                                            parts                                                                               14.2                    0.5 part                                                                   __________________________________________________________________________

Appliction Example 14

To 1 part of a chromium complex represented by the formula: ##STR118## 100 parts of a styrene-n-butyl methacrylate copolymer and 8 parts of carbon black were added and thoroughly mixed. The mixture was then kneaded while heating and melting it. After cooling, the mixture was roughly pulverized in a mixer, and then finely pulverized by a high speed centrifugal pulverizer to obtain a positively chargeable fine toner. The toner was mixed with iron powder having a particle size of from 100 to 150 μm in a weight ratio of 5:100, and the mixture was used for a commercially available copying machine employing a zinc oxide photosensitive material, whereby a clear image free from fogging was obtained. The quantity of the electric charge of the toner was 17.5 μc/g on an average as measured by a blow off method, and the electric charge distribution was substantially uniform at a level of from 17.0 to 18.3 μc/g.

Application Examples 15 to 29

In the same manner as in Example 14, toners containing metal complexes and having compositions as identified in Table 4 were obtained. The electric chargeability of these toners were measured. The results are also shown in the Table 4.

                                      TABLE 4                                      __________________________________________________________________________                                                                Elec-               Appli-                                                     tric                cation                                                     charge-             Exam-                                                                              Composition of the developer                           ability             ples                                                                               Metal complex                            Other components                                                                             (μc/g)           __________________________________________________________________________     15                                                                                  ##STR119##                              Styrene-ethyl- hexyl metha-                                                    crylate Polyester resin                                                        Silicone wax Carbon black                                                      Iron powder carrier                                                                    40 parts 5 parts 3                                                             parts 2 parts 1000                                                             parts 14.8                    0.2 part                                                                   16                                                                                  ##STR120##                              Styrene-acryl copolymer                                                        Carbon black Glass beads                                                       carrier 30 parts 3 parts                                                               1000                                                                                 18.9s                   0.5 part                                                                   17                                                                                  ##STR121##                              Styrene-methyl methacrylate                                                    copolymer Silicone resin-                                                      coated iron powder                                                                     50 parts 1500                                                                        16.3s                   10 parts                                                                   18                                                                                  ##STR122##                              Polyvinyl butyral resin                                                        Carbon black Iron powder                                                       carrier 200 parts 10 parts                                                             2000                                                                                 17.4s                   2 parts                                                                    19                                                                                  ##STR123##                              Bisphenol type epoxy resin                                                     Carbon black Iron powder                                                       carrier 50 parts 2 parts                                                               1000                                                                                 18.6s                   0.5 part                                                                   20                                                                                  ##STR124##                              Styrene resin Carbon black                                                     Iron powder carrier                                                                    50 parts 2 parts                                                               1000                                                                                 14.0s                   0.5 part                                                                   21                                                                                  ##STR125##                              Styrene-butyl methacrylate                                                     copolymer Carbon black Iron                                                    powder carrier                                                                         30 parts 2 parts 800                                                           parts 15.0                    0.2 part                                                                   22                                                                                  ##STR126##                              Phenol resin Polyester resin                                                   arbon black  Silicon resin-                                                    coated iron powder                                                                     15 parts 8 parts 2                                                             parts 700                                                                            21.3s                   0.5 part                                                                   23                                                                                  ##STR127##                              Polyethylene wax Ethylene-                                                     vinyl acetate copolymer                                                        Magnetite                                                                              50 parts 40 parts 30                                                           parts 18.5                    1 part                                                                     24                                                                                  ##STR128##                              Styrene-ethyl- hexyl metha-                                                    acrylate copolymer Carbon                                                      black Ironpowder carrier                                                               20 parts 1 part 600                                                            parts 23.2                    0.5 part                                                                   25                                                                                  ##STR129##                              Maleic acid resin Carbon                                                       black Iron                                                                             50 parts 5 parts                                                               1000                                                                                 16.4s                   0.2 part                                                                   26                                                                                  ##STR130##                              Styrene-ethyl methacrylate                                                     copolymer Carbon black Iron                                                    powder carrier                                                                         30 parts 3 parts 500                                                           parts 18.3                    0.1 part                                                                   27                                                                                  ##STR131##                              Styrene-buta- diene co-                                                        polymer Carbon black Iron                                                      powder carrier                                                                         50 parts 5 parts                                                               1500                                                                                 16.7s                   1 part                                                                     28                                                                                  ##STR132##                              Polyester resin C.I. pigment                                                   lue-15 Silicone resin-                                                         coated iron powder                                                                     12 parts 0.2 part                                                              400                                                                                  18.5s                   0.4 part                                                                   29                                                                                  ##STR133##                              Styrene-butyl methacrylate                                                     copolymer Carbon black Iron                                                    powder carrier                                                                         100 parts 5 parts                                                              300                                                                                  17.2s                   2 parts                                                                    __________________________________________________________________________ 

I claim:
 1. A symmetric 2:1 metal complex represented by the general formula: ##STR134## where R is a hydrogen atom, an alkyl group having from 1 to 10 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an alkoxycarbonyl group having from 2 to 5 carbon atoms, an acyl group having from 2 to 5 carbon atoms, an aminocarbonyl group, an alkylaminocarbonyl group having from 2 to 5 carbon atoms, an alkylsulfonyl group having from 1 to 3 carbon atoms, an aminosulfonyl group, an acylamino group having from 2 to 5 carbon atoms, a nitro group, a cyano group or a halogen atom, m is an integer of from 1 to 4, when m is 2 or more, the plurality of R may be the same or different substituents, Q is --NHCO--Y--Z or --CONH--Y--Z (where Y is an alkylene group having from 1 to 4 carbon atoms, and Z is a quaternary ammonium group), M is a chromium atom or a cobalt atom, and X.sup.⊖ is an anion.
 2. The metal complex according to claim 1, wherein X.sup.⊖ is a halogen ion.
 3. An electrophotographic toner containing from 1 to 50% by weight of the metal complex of the formula I as defined in claim 1, and from 50 to 99% by weight of a resin.
 4. The electrophotographic toner according to claim 3, wherein the resin is a styrene polymer, a substituted styrene polymer, a styrene-substituted styrene copolymer, a styrene-acrylate copolymer, a styrene-methacrylate copolymer, a styrene-acrylonitrile copolymer, a polyvinyl chloride resin, a polyethylene resin, a silicone resin, a polyester resin, a polyurethane resin, a polyamide resin, an epoxy resin, a modified rosin or a phenol resin. 